1. Field of the Invention
The field of the invention relates generally to the clinical use of a laser delivery device which may be coupled to a stereomicroscope or camera equivalent, or coupled to protective mirrors and/or filters.
2. Description of Related Art
Laser surgery generally requires the treating physician to illuminate and view the treatment site, and irradiate the treatment site with a laser beam. In various medical applications such as ophthalmology, neurology, dermatology or ear, nose and throat procedures, the physician typically views the treatment site through a stereomicroscope along a viewing axis within a magnified field of view. The physician may then activate the laser to irradiate the desired location.
In some existing systems, the laser delivery device is hand-held whereby the physician manually directs the laser beam to the desired location while viewing the treatment site through the stereomicroscope. This arrangement however, may not be suitable for medical applications requiring a high degree of accuracy such as procedures in the medical fields listed above.
Furthermore, a physician may desire to move the viewing axis to view different areas of the treatment site and at the same time, irradiate with the laser beam, the precise locations being viewed. Because the hand-held laser is not fixedly positioned with respect to the stereomicroscope, the laser beam cannot track along with the viewing axis as it is moved across the treatment site.
Other existing systems incorporate the laser delivery device so that it is not held by hand thereby increasing accuracy. In ophthalmic laser surgery for example, the physician typically employs a slit-lamp which includes a stereomicroscope as well as a micromanipulator which directs the laser beam to the treatment site. In this arrangement, the micromanipulator is fixedly positioned in relation to the stereomicroscope which allows the laser beam to track along with the viewing axis as it is moved.
However in systems where the laser delivery device is fixedly positioned relative to the stereomicroscope, the laser beam is typically coaxially aligned with the viewing axis, or may be moved only slightly from coaxial alignment. This limitation may prevent the treating physician from viewing the treatment site at one angle while irradiating it from another. This in turn limits flexibility in treating "hard to reach" areas such as the filtration angle of the anterior chamber of an eye. In dealing with this problem, some existing ophthalmic systems employ contact lenses which may direct the laser beam to the relatively inaccessible area. However, contact lenses generally increase the difficulty of the ophthalmic procedure being performed and may cause discomfort to the patient. While some systems may allow the laser delivery device to be positioned at an angle to the viewing axis, these systems usually provide only a limited range of angles thereby still limiting the flexibility of clinical treatment.
Where the laser delivery device is fixedly positioned in the system, limitations on flexibility in treatment also arise in connection with the characteristics of the laser beam itself. Because the laser delivery device is fixed, the focal length (working distance), cone angle, spot size and power density of the laser beam may also be limited. Thus, for example, if the physician must irradiate another treatment site located at a different distance from the system, time-consuming adjustments to vary focal length may be necessary. Furthermore, while in the ophthalmic field for example, contact lenses may be used to adjust these laser beam parameters, contact lenses generally increase the difficulty of the ophthalmic procedure.
With regard to safety, existing systems may employ fixed or movable filters, shutters, and/or dichroic mirrors to block, split or otherwise modify the laser beam which typically comprises multiple wavelengths. Dichroic mirrors may reflect the wavelength to be used for treatment onto the treatment site while absorbing other wavelengths so that the physician may view the treatment site during irradiation. Filters may also be used to protect the physician from potentially harmful wavelengths. Alternatively, a shutter may be used to completely block the physician from the laser beam.
Because filtering is not 100% efficient however, if the physician is to view the treatment site while irradiation occurs, the physician may be exposed to a fraction of undesired wavelengths. In fact, there are reports that physicians chronically exposed to slight amounts of blue wavelengths suffer from a change in color vision. Accordingly, dark filters which reduce or block different wavelengths have been used. However, dark filters greatly impair or distort the physician's field of view. Furthermore, shutters prevent the physician from viewing the treatment site during irradiation. Still further, existing systems may require an activation mechanism so that the filter or shutter blocks the viewing axis before the laser fires. Besides adding another step in the medical procedure, if this mechanism fails the physician may be exposed to harmful wavelengths.
In existing systems built for a specific laser such as an Argon blue/green laser, the mirror/filter network may have little or no effect on other wavelengths such as yellow. This is because current filters and dichroic mirrors are designed to filter or otherwise accommodate only specific wavelengths of light. Thus, if a Krypton yellow laser were mistakenly attached to a system intended for use with an Argon blue/green laser, the mirrors and filters designed to prevent transmission of the blue light would still allow yellow wavelengths to be transmitted which may result in harm to the patient or physician.
In light of the foregoing, there is a need for a laser delivery system which may be positioned at various angles and distances relative to the treatment site as well as at various angles to the viewing axis and which may track along with the viewing axis. There is also a need for a laser delivery system which includes a filter/mirror safety system to protect both the patient and treating physician.